This letterbook covers the period March-October 1886. Many of the letters are by Edison. There is also correspondence by Samuel Insull and Alfred O. Tate. Most of Edison's letters are in the hand of Insull or John F. Randolph, acting as Edison's secretary. The correspondence relates to a variety of subjects. Some letters pertain to the financial affairs of Edison-affiliated companies, including the Edison Machine Works and the Edison Electric Light Co. of Europe, Ltd. There is also correspondence dealing with the development of Edison's phonoplex telegraph system in North America and the United Kingdom, with American and foreign patent matters, and with Edison's property in Fort Myers, Florida. Included also are a few letters from Insull and Tate to Edison. Among the recipients are the Edison & Swan United Electric Light Co., Edward H. Johnson, and Robert H. Thurston. The front cover is marked "1886." The spine is stamped "Letters." The book contains 491 numbered pages and an index. There are also numerous groups of unnumbered pages inserted into the book between the numbered pages. Approximately 30 percent of the book has been selected.